TM 5-3820-245-14&P
in the water in the container during engine operation will indicate this leakage. Another method for observing air in the
cooling system is by inserting a transparent tube in the water outlet line.
Drain Cooling System
The engine coolant is drained by opening the cylinder block and radiator (heat exchanger) drain cocks and removing the
cooling system filler cap. Removing of the filler cap permits air to enter the cooling passages and the coolant to drain
completely from the system.
The 3-53 cylinder block has a drain cock or plug located on the side of the block opposite the oil cooler.
NOTE
Drain cocks or plugs on both sides of the engine must be opened to drain the engine completely.
In addition to the drains on the cylinder blocks, the In-line engines have a drain cock located on the bottom of the oil cooler
housing. Radiators, etc., that do not have a drain cock, are drained through the oil cooler housing drain.
To insure that all of the coolant is drained completely from an engine, all cooling system drains should be opened. Should
any entrapped water in the cylinder block or radiator freeze, it will expand and may cause damage. When freezing
weather is expected, drain all engines not adequately protected by antifreeze. Leave all of the drain cocks open until
refilling the cooling system.
Raw water pumps are drained by loosening the cover attaching screws. It may be necessary to tap the raw water pump
cover gently to loosen it. After the water has been removed, tighten the screws.
Flushing
The cooling system should be flushed each spring and fall. The flushing operation cleans the system of antifreeze solution
in the spring and removes the summer rust inhibitor in the fall, preparing the cooling system for a new solution. The
flushing operation should be performed as follows:
1. Drain the previous season's solution from the engine.
2. Refill the cooling system with soft clean water. If the engine is hot, fill slowly to prevent rapid cooling and distortion
of the engine castings.
3. Start the engine and operate it for 15 minutes to circulate the water thoroughly.
4. Drain the cooling system completely.
5. Refill the system with the solution required for the coming season.
PAGE 132
